1. Field of the Invention
The present invention relates to a remote center compliance device. More particularly, the present invention relates to a remote center compliance device with one elastic body, in which an elastic center can be formed using one elastic body and the adjustment of the elastic center is easy. Further, since the number of parts is minimized, a manufacturing cost and a manufacturing process are reduced and an efficiency of installation space is maximized, thereby improving product competitiveness.
2. Description of the Related Art
Generally, a remote center compliance device is a device that makes it easy to perform an assembly work by correcting a center error between a boss and an axis during an insertion work of the boss and axis by using an elastic enter principle.
The elastic center principle is a mechanical principle that when an elastic center is located near an object confined in the remote center compliance device and an external force acting on the object passes through the elastic center, the object supported to the remote center compliance device performs only a translation in a direction of the external force without any rotation and, when a moment acts on the elastic center, the object performs only a rotation centering on the elastic center without any translation.
FIG. 1 is a front view illustrating a center error and a repulsive force between parts during an assembly process in a conventional remote center compliance device, and FIG. 2 is a front view illustrating a center error correcting process and an assembly process in a conventional remote center compliance device.
Referring to FIGS. 1 and 2, the conventional remote center compliance device 1 includes upper and lower structures 2 and 3 and a plurality of elastic bodies 4 provided between the upper and lower structures 2 and 3.
Upon operation of the conventional remote center compliance device, when a shaft 6 held by a grippe 8 attached to the bottom of the lower structure 3 is moved downward in a direction V so as to insert it into a shaft hole 7 a front end of the shaft 6 1-point contacts a champered portion of the shaft hole 7.
At this point, the contact force R between the parts is defined by a horizontal component force Rx and a vertical component force Rz. When the remote center compliance device is designed such that its elastic center P is placed at an end of a part, the horizontal component force Rx passes through the elastic center P, so that the shaft 6, the gripper 8 and the lower structure 3 perform only a translation in horizontal direction without causing a rotation.
Therefore, the shaft 6 is inserted into the shaft hole 7 while performing a translation within a center error (e) with respect to the shaft hole 7.
When a precise part such as a precise shaft, a pin, and a bearing is inserted by an industrial robot or a dedicated assembly apparatus using the above-described remote center compliance device, an excessive insertion force which may occur due to a center error or angle error between assembly parts can be prevented in advance. Therefore, d\part damages can be suppressed, product quality and work efficiency can be improved, and a high-precision assembly line can be co constructed at a low cost.
However, the conventional remote compliance device has drawbacks in that it is difficult to correctly adjust the elastic center P, which is the essence of the elastic center principle, the number of parts is large, and the manufacturing and assembly processes are complicated.
The process error is caused by the manufacture error of the parts, i.e., the upper and lower structures 2 and 3 and a plurality of elastic bodies 4, and the cumulative error is caused by an assembly error generated when the parts are assembled. Therefore, the elastic center P calculated in the initial design and the elastic center P after the assembly are moved by the cumulative error. In this case, when the elastic centers P are not correctly adjusted, the shaft 6 below the lower structure 3 performs a rotation without any translation. Hence, the error (e) between the centers of the shaft 6 and the shaft hole 7 is not corrected; rather, a jamming phenomenon at the entrance of the shaft hole occurs.
In particular, the elastic bodies 4 are manufactured by stacking a plurality of metal disks at constant intervals and filling a rubber between the stacked metal disks. A stack error occurs when the plurality of metal disks are stacked. Further, due to the use of the elastic disks 4 having the stack error, it is difficult to fin the elastic center P on a line of the central shaft of the remote center compliance device.
Moreover, during the insertion process of inserting the precise parts such as a precise shaft, a pin, and a bearing, it is difficult to measure the insertion force for the insertion process. Therefore, the precise parts are damaged by a new excessive insertion force. During the error correction for matching the center, the measurement of the error value of the remote center compliance device for the error correction is difficult. Hence, the error must be always corrected.